1 #include <cstdio>
 2 #include <algorithm>
 3 using namespace std;
 4 const int N = 500010;
 5 struct Edge
 6 {
 7     int u,v,next;
 8 }edge[N<<1];int top;
 9 int point[N],fa[N][30],deep[N],md,n;
10 inline void add(int x,int y)
11 {
12     top++;
13     edge[top].u=x;
14     edge[top].v=y;
15     edge[top].next=point[x];
16     point[x]=top;
17     return;
18 }
19 void dfs(int op,int d)
20 {
21     deep[op]=d;
22     int ed,i=point[op];
23     while(i)
24     {
25         ed=edge[i].v;
26         if(deep[ed]) fa[op][0]=ed;
27         else dfs(ed,d+1);
28         i=edge[i].next;
29     }
30     return;
31 }
32 void pre_lca()
33 {
34     for(int j=1;j<=md;j++)
35     {
36         for(int i=1;i<=n;i++) fa[i][j]=fa[fa[i][j-1]][j-1];
37     }
38     return;
39 }
40 int lca(int x,int y)
41 {
42     if(deep[x]>deep[y]) swap(x,y);
43     for(int i=md;i>=0;i--)
44     {
45         if(deep[fa[y][i]]>deep[x])  y=fa[y][i];
46         else if(deep[fa[y][i]]==deep[x]){y=fa[y][i];break;}
47     }
48     if(deep[x]!=deep[y]) y=fa[y][0];///this!！！！！！！
49     if(x==y) return x;
50     for(int i=md;i>=0;i--)
51     {
52         if(fa[x][i]!=fa[y][i]) {x=fa[x][i];y=fa[y][i];}
53     }
54     return x==y?x:fa[x][0];
55 }
56 int main()
57 {
58     int m,r;
59     scanf("%d%d%d",&n,&m,&r);
60     while((1<<md)<=n) md++;///this!
61     md--;
62     int x,y;
63     for(int i=1;i<n;i++)
64     {
65         scanf("%d%d",&x,&y);
66         add(x,y);
67         add(y,x);
68     }
69     dfs(r,1);
70     pre_lca();
71     while(m--)
72     {
73         scanf("%d%d",&x,&y);
74         printf("%d\n",lca(x,y));
75     }
76 
77     return 0;
78 }